Various methods are known for initiating combustion in an internal combustion engine. Certain conventional methods consist in initiating combustion of the mixture locally either by generating a spark therein (controlled ignition), or by locally enriching the mixture so as to give rise to charge-compression ignition thereof. Combustion of the remainder of the mixture is then obtained either by propagation of a flame front, or by flame diffusion.
Recently, development effort has been applied to combustion by homogeneous charge-compression ignition (HCCI) which appears to be promising in terms of energy efficiency and in terms of preserving the environment.
Nevertheless, although homogeneous charge-compression ignition can be achieved nowadays over a narrow engine operating range, it is found difficult to achieve over a broad operating range. Homogeneous charge-compression ignition requires very tricky management of starting and of combustion progression. Present research is thus directed to very fine management of the thermodynamic conditions of the mixture (adapting the fuel, admission temperature, complex management of exhaust gas recirculation), or to introducing complex technologies such as variable compression ratios or variable distribution.
The invention seeks to provide a method of combustion by charge-compression ignition that is easily adaptable and that can be used over a wide operating range of the engine.
The following documents FR 2 078 819, EP 0 953 744, U.S. Pat. No. 4,282,845, and DE 39 03 474 disclose engines comprising:                a main chamber of variable volume into which an ignitable mixture is introduced;        an auxiliary chamber opening out into the main chamber; and        controlled means for putting the auxiliary chamber into communication with the main chamber, or for isolating it therefrom;        